As it is known, the children are instinctively in the habit to put into their mouth any object they can have on hand, seriously risking that said objects could be swallowed, obstructing the respiratory tract. In this last case there can be deadly consequences provided if is not possible to have at one's disposal a medical aid in a very short lapse of time.
Among the various objects that are widespread to day and even offered to children to enjoy themselves, writing instruments have to be included such as felt pens, ballpoint pens and the like, the most dangerous part of which is constituted by the closing cap that has dimensions limited enough it could be easily swallowed. For this reason the manufactures of writing instruments are engaged to provide suitable means to prevent the suffocation of children who swallowed such caps, allowing an even limited flow of air such as to consent to breath during a lapse of time sufficient for the intervention of medical personnel able to carry out the elimination of the occlusion.
GB Patent Application No. 2,174,374 to Balls discloses a hollow detachable closure cap for the container of a liquid or paste product comprising an open ended base constituting locating means for the cap on the container and a part with a closed end extending axially from the base; the part being formed with external longitudinally extending ribs separated by recesses; the base wall of at least one of the recesses adjacent the base being formed with a longitudinal slot and the end of the part nearest its closed end constituting a seal for the container.
A serious drawback of this closure cap is the fact that the slots are obtained in the circumferential face of the substantially cylindral part of the cap joining the two ends.
As a consequence, only with a truncated cone cap a negligeable part of the air, coming in from the bottom open end, could follow a straight path and come out through the lateral slots to keep in touch with the outer wall of the cap between the recesses obtained between two adjacent openings.
The remaining air coming in from the opening at the cap base, which is most of it, is sent to the cap holes through tortuous paths.
On the other hand, if the cap is cylindrical, all the air coming in from the base would come out of the slots through tortuous paths.
On the contrary it is fundamental for the air coming in from the base, all or most of it, to follow a straight path as it has to reach as quickly as possible, and in the largest quantity over possible, the throat of the person who has swallowed.